docs: record GIF/embed fixes, Synapse 1.157.1 caps, MSC4354 decision

- Mark the desktop Tauri CSP frame-src finding FIXED (cinny-desktop daba59b).
- Add the GIF-animation fix + Mixcloud/Deezer embeds write-up (4154cae5),
  incl. the Deezer /show vs /podcast correction.
- New section: Matrix 2.0 call membership (MSC4354 sticky events) —
  investigated across 3 agents, deliberately NOT enabled. Records why the
  server flag is a no-op alone (EC gates it behind a per-device developer
  setting defaulting to Legacy), what was verified safe, and the one open
  risk (lk-jwt-service LiveKit-alias mapping across the two JWT endpoints)
  that a two-account test call must settle before any rollout.
- Refresh Server Capabilities: Synapse 1.157.1, MSC list re-dumped live from
  /_matrix/client/versions, note that msc4143 is not a real gap (LiveKit is
  discovered via .well-known) and that msc3861 client code is now dead.
- Note the blocked-feature re-check found no change on 1.157.1.
- Drop a verbatim-duplicated "remaining providers" heading; provider count
  16 -> 18.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

LOTUS_TODO.md

@@ -97,7 +97,7 @@ Per-slice bug hunt (5 agents: theming · calls · messaging · threads/presence/
 
 **Embeds / URL previews**
 
-- [ ] **[Med] Desktop (Tauri) CSP `frame-src` is missing `store.steampowered.com`, `www.mixcloud.com`, `widget.deezer.com`** → the Steam widget (shipped) + new Mixcloud/Deezer embeds are silently blocked (blank iframe) **in the desktop app** (`cinny-desktop/src-tauri/tauri.conf.json`). Web is fine (`frame-src 'self' https:`). Add the three hosts (`frame-src` only — no `connect-src`; these don't do a client oEmbed fetch). **Verified.**
+- [x] **[Med] Desktop (Tauri) CSP `frame-src` was missing `store.steampowered.com`, `www.mixcloud.com`, `widget.deezer.com`** → the Steam widget (shipped) + new Mixcloud/Deezer embeds were silently blocked (blank iframe) **in the desktop app**. **FIXED** (`cinny-desktop` `daba59b`): all three added to `frame-src` (no `connect-src` — these don't do a client oEmbed fetch). Web was always fine (`frame-src 'self' https:`). Needs desktop-app QA to confirm the widgets render.
 - [ ] **[Low]** `searchCache.ts` encrypted-search index has no size/count cap — unbounded on-disk growth (mitigated by the manual "Clear cached index" + logout wipe).
 - [ ] **[Low]** `MsgTypeRenderers.tsx` `MLocation` OSM permalink uses raw `geo:` lat/lon substrings, not the validated floats — harmless (URL context, malformed input only).
 
@@ -193,6 +193,18 @@ Genuine Matrix client-spec / MSC features Lotus does **not** yet implement (audi
 
 **Server-gated / advanced (capture, don't build yet):** QR sign-in for a new device (**MSC4108** rendezvous — needs an HS-side endpoint); dehydrated devices (**MSC3814** — offline key delivery, also helps the E2EE KE cluster); E2EE history key sharing on invite (**MSC3061** `shared_history`, niche); voice broadcast (Element MSC3888, low value — skip).
 
+### [ ] Matrix 2.0 call membership — MSC4354 sticky events (INVESTIGATED 2026-07, deliberately NOT enabled)
+
+3-agent investigation after the 1.157.1 upgrade (EC-fork behavior · Synapse/upstream readiness · client-fleet composition). **Conclusion: leave `msc4354_enabled` OFF for now** — enabling it is safe but delivers **zero user-visible benefit on its own**, and introduces a latent footgun.
+
+**Why it's a no-op alone:** the EC fork's `doesServerSupportUnstableFeature(MSC4354)` probe feeds **exactly one thing** — whether the "Matrix 2.0" radio in **Developer Settings** is greyed out (`DeveloperSettingsTab.tsx:349-353`). The real switch is the per-device `matrixRTCMode` setting (`settings.ts:149-152`), which **defaults to `Legacy`** and never auto-enables. Sticky sending is gated at `LocalMember.ts:862` (`unstableSendStickyEvents: mode === Matrix_2_0`). So flipping the server flag changes nothing any client sends.
+
+**Verified safe:** Synapse-side is **additive and cleanly reversible** — the `sticky_events` schema ships unconditionally (no migration/backfill on enable), every write/read/serialize/replication path is flag-gated, disabling stops it instantly and residual rows self-expire ≤1h. The one relevant bug (#19787 `/sync` EDU-filter) was fixed in 1.155.0; the SQLite<3.40 guard doesn't apply (we're on PG 17.10). Matrix-layer **mixed-mode visibility is safe**: js-sdk `collectMembersEvents` reads **both** sticky and state membership and merges them, so sticky-mode and legacy-mode participants see each other. Our `lk-jwt-service` already serves **both** JWT endpoints (legacy `/sfu/get` **and** the sticky-mode `/get_token` — both probed live, 400-with-validation-error = present). EC is bundled into cinny's build (`@lotusguild/element-call-embedded`), so the fleet upgrades **atomically** — the "all EC clients ≥ v0.17.0" precondition is structurally guaranteed for our own users.
+
+**The one unresolved risk (blocks a real rollout, not the flag):** sticky mode drops `livekit_alias` and uses `/get_token` (slot `m.call#ROOM`) while legacy uses `/sfu/get` (`room=roomId`). **Whether both resolve to the same LiveKit room is a property of lk-jwt-service, not the client** — unverified. If they diverge, cross-mode participants appear in each other's member list but are **split at the media layer** (silent, no error). Requires a **two-account test call** (one device on Legacy, one on Matrix 2.0) to confirm before anyone relies on it.
+
+**If we ever do this:** (1) run the two-account media-interop test; (2) only then consider enabling `msc4354_enabled: true` in `/etc/matrix-synapse/homeserver.yaml` (LXC 151) + restart; (3) treat a default-mode change as a separate coordinated EC rollout. MSC4354 is still **OPEN upstream** (not in FCP, `needs-implementation`), so this stays experimental regardless.
+
 ### Remaining spec/MSC gaps (2026-07 full-surface survey)
 
 After Phases A–C the client spec is ~complete. What's left, flagged by **what unblocks it**:
@@ -265,11 +277,7 @@ Intentional desktop deltas (disclosed, non-regressive): volume sliders below lab
 
 ### [ ] Inline media embeds — remaining providers (LOW PRIORITY)
 
-The inline embed system (`videoEmbed.ts`) covers 16 providers; three more were **deliberately deferred** (verified against 2026 docs by review agents):
-
-### [ ] Inline media embeds — remaining providers (LOW PRIORITY)
-
-The inline embed system (`videoEmbed.ts`) covers 16 providers; three more were **deliberately deferred** (verified against 2026 docs by review agents):
+The inline embed system (`videoEmbed.ts`) covers 18 providers (16 + Mixcloud/Deezer); three more were **deliberately deferred** (verified against 2026 docs by review agents):
 
 - **Bandcamp** (highest-value audio add) — needs an **oEmbed** round-trip: the player URL requires numeric `album`/`track` item ids that aren't in the page URL (`bandcamp.com/oembed` is the resolver; mirror the `TikTokEmbedCard` on-click oEmbed pattern). CSP `frame-src`: `bandcamp.com`. Classify `kind: 'audio'`.
 - **SoundCloud `on.soundcloud.com` short links** — the `w.soundcloud` widget resolver does **not** follow the redirect; needs the same on-click oEmbed resolve (`soundcloud.com/oembed`, CORS-enabled) to get the canonical URL. (Canonical `soundcloud.com/{user}/{track}` links already work.)
@@ -279,6 +287,8 @@ Also open (from the quality review): a real `onError`/error-state fallback for i
 
 **✅ Steam detailed embed (2026-07, 2-agent review) — `ef82650c`.** `store.steampowered.com` content URLs get rich cards: **app** pages → OG capsule header + click-to-play facade → Steam's official `/widget/{id}` store iframe (live region-aware price / discount % / Buy on Steam, gated by `inlineMediaEmbeds`); **news/announcement** → banner + headline + body-preview card; **bundle/sub/dlc** → OG store card. `getSteamTarget`/`steamWidgetEmbedUrl` in `videoEmbed.ts` (+tests). Grounded in prod CSP (`frame-src https:` allows the widget with no infra change; images via homeserver `mxc`; NO client-side Steam API — `connect-src` + Steam CORS both block it, which is the honest ceiling: no review scores/genres/screenshots client-side). **Needs on-device QA:** the live widget iframe height/fit (can't render headlessly) — verify the price/Buy stay visible on desktop-wide and phone.
 
+**✅ GIF previews now animate + Mixcloud/Deezer embeds (2026-07, 2-agent review) — `4154cae5`.** Reported live: a `media.giphy.com` link "shows the gif's image but doesn't play it." Root cause: **Synapse's `/thumbnail` endpoint flattens animated GIFs to a still first frame**, and every preview image went through it. `GifCard` (Giphy/Tenor) + the generic OG card now request the **original** via `/download` (`mxcUrlToHttp` with no width/height) when the preview is a GIF (`og:image:type === 'image/gif'` or a `.gif` pathname). Guarded: `shouldServeGifOriginal()` keeps the frozen thumbnail past a **10 MB** `matrix:image:size` cap, and the generic card's eager `<img>` gained the `loading="lazy"` it was the only preview image missing. Also added **Mixcloud + Deezer** audio embeds, and fixed Deezer podcasts (they live at `/show/<id>`, **not** `/podcast/<id>` — the latter 404s on Deezer's own oEmbed; verified against the live API). **Needs on-device QA:** confirm a large GIF still animates and doesn't stall the timeline.
+
 **✅ Embed bug hunt (2026-07, 3 survey agents + 2-agent review) — `f2673eff`.** Core posture verified **sound** (iframe sandbox, `useIframeAutoHeight` postMessage origin+source trust, no XSS/`dangerouslySetInnerHTML`, `rel="noreferrer"` on all 21 links, oEmbed no-SSRF, the whole facade→iframe/abort/observer lifecycle). Fixed: Twitch/Kick/SoundCloud/Streamable reserved-path over-match (utility pages rendered as broken players), Vimeo hash over-capture (`[0-9a-f]{6,}`), Spotify/Steam/Discord/IMDb `og:image` now via `mxcUrlToHttp` (was a broken raw `mxc://` `<img>` + a pre-click 3p-request facade bypass), `wide` class follows the og:url-resolved embed, Twitter host alignment (`mobile.twitter.com`/`/statuses/`), URL de-dupe.
 
 **Deferred / surfaced from the hunt (not fixed — decide before doing):**
@@ -296,7 +306,7 @@ Also open (from the quality review): a real `onError`/error-state fallback for i
 
 ## 🚫 Blocked Features (server / upstream gated)
 
-Re-run `/_matrix/client/versions` + `unstable_features` after each Synapse upgrade.
+Re-run `/_matrix/client/versions` + `unstable_features` after each Synapse upgrade. **Re-checked on 1.157.1 (2026-07-23): no change — all four below are still `false`.** The 1.156.0→1.157.1 delta unblocked nothing (it's a bugfix release; the only feature-bearing release in the gap was 1.156.0, which we were already running).
 
 - **[BLOCKED] Live Location Sharing** (MSC3489 + MSC3672 both `false`) — real-time GPS beacons over the existing static share.
 - **[BLOCKED] Reaction/Relation Redaction** (MSC3892 `false`) — remove a reaction without redacting the parent; current full-redaction fallback is acceptable.
@@ -309,8 +319,9 @@ Re-run `/_matrix/client/versions` + `unstable_features` after each Synapse upgra
 
 ### Server Capabilities (as of 2026-07)
 
-- **Homeserver** `matrix.lotusguild.org` · **Synapse** `1.156.0+trixie1` (upgraded 2026-07-07 from 1.155; apt package on Debian 13, LXC 151) · **Matrix spec** up to `v1.12` (Synapse still advertises v1.12; MSC features via `unstable_features`).
-- **MSC ON:** `msc4140` · `msc3771` · `msc3440.stable` · `msc4133.stable` · `simplified_msc3575` · `msc4222` · `msc3266` (room summary live at unstable `im.nheko.summary/summary/{id}` — 200; the `/v1/rooms/{id}/summary` path is still 404) · `msc3401_matrix_rtc`. **OFF/blocked:** `msc4306` · `msc3882` · `msc3912` · `msc4155` · `msc3489`/`msc3672` · `msc3892`.
+- **Homeserver** `matrix.lotusguild.org` · **Synapse** `1.157.1+trixie1` (upgraded 2026-07-23 from **1.156.0** — note the host was found on 1.156.0 while the docs claimed 1.155.0, so **always verify with `dpkg-query -W matrix-synapse-py3`**, don't trust the docs; apt package on Debian 13, LXC 151) · **Matrix spec** up to `v1.12` (Synapse still advertises v1.12; MSC features via `unstable_features`).
+- **MSC ON** (re-dumped live from `/_matrix/client/versions` on 1.157.1): `msc4140` · `msc3771` · `msc3440.stable` · `msc4133.stable` · `simplified_msc3575` · `msc4222` · `msc3266` (room summary live at unstable `im.nheko.summary/summary/{id}` — 200; the `/v1/rooms/{id}/summary` path is still 404) · `msc3401_matrix_rtc` · `msc2285.stable` · `msc3827.stable` · `msc3981` · `msc4380.stable` · `msc4445` · `msc2659.stable` · `msc2666` · `msc2432` · `e2e_cross_signing` · `label_based_filtering`. **OFF/blocked:** `msc4306` · `msc3882` · `msc3912` · `msc4155` · `msc3489`/`msc3672` · `msc3892` · `msc4028` · `msc4069` · `msc4108` · `msc3391` · `msc4354` (sticky events — **deliberately off**, see the Matrix 2.0 section above) · `msc4143` (RTC foci — **not a gap**: LiveKit is discovered via `.well-known` `org.matrix.msc4143.rtc_foci`, confirmed live, not this flag).
+- **Dead client code:** Synapse 1.157.0 **removed** `msc3861` (MAS auth delegation) entirely — the ~6 `msc3861`/`msc2965` references in `src/` can never activate against this homeserver (we auth via Authelia `oidc_providers`). Harmless, but cleanup material.
 - **Live endpoints:** Report User (MSC4260) **200** ✅ · Report Room (MSC4151) ✅.
 - **Homeserver access (audits):** Synapse = LXC 151 (`pct exec 151 -- bash`), config `/etc/matrix-synapse/homeserver.yaml`. Web deploy = LXC 106. Voice guard = `voice-limit-guard.py` on LXC 151.
 - **SDK notes:** no arbitrary profile-field methods (use `mx.http.authedRequest()` for MSC4133); js-sdk can't per-room filter `/sync`; sanitizer strips `<math>`/MathML; SW exists at `src/sw.ts`; `getMatrixToRoom()` builds invite URLs; EC audio-inject unblocked via the fork's `io.lotus.inject_audio`.